1. Field of the Invention
The present invention relates to an optical adapter, and more particularly to an optical adapter for a camera having a cylindrical lens to form an image in which vertical and horizontal magnifications are different, and a lens-fitted photo film unit to which the optical adapter is attached.
2. Description of the Prior Arts
In order to apply a visual effect in a photographed picture, it is known to attach an optical adapter to a front surface of a taking lens in photographing a human subject. For example, there is an optical adapter which makes the human subject look thinner or fatter than actual. Such optical adapter is disclosed in U.S. Pat. No. 6,072,636 and Japanese Patent Laid-Open Publication No. H11-64962, and so on. The optical adapter disclosed in these publications forms an image so as to differentiate vertical and horizontal magnifications of the human subject by using a cylindrical lens.
In Japanese Patent Laid-Open Publication No. 2000-122233, the cylindrical lens as the optical adapter is provided in a lens-fitted photo film unit into which an unexposed photo film is pre-loaded. The optical adapter can differentiate the vertical and horizontal magnifications of the subject image in the photo film.
In the optical adapter described in the above-mentioned publications, however, the taking lens is covered by the cylindrical lens, while a viewfinder is not. Accordingly, in the event of using a normal camera or a lens-fitted photo film unit except for a single-lens reflex camera, a photographer cannot confirm the change in the vertical and horizontal magnifications through the viewfinder. If the photographer takes a photograph without being aware that the optical adapter is attached to the camera, it is caused to make a printed photograph which is not intended by the photographer.
In Japanese Patent Laid-Open Publication No. 2000-122233, the viewfinder is covered by the cylindrical lens. However, since the taking lens and the viewfinder are respectively covered by different cylindrical lenses. It is necessary to cover the taking lens and the viewfinder separately. Such operation is troublesome, and may cause a mistake.